The invention relates to an arrangement for producing package spools used as feeding packages for twisting onto which two yarns are wound side by side, having drafting units for two slivers, having air nozzles for strengthening the slivers to form yarn components, and having yarn guides for the guiding-together of the yarn components to form a double yarn. A withdrawal device is provided for withdrawing the double yarn which has a wind-up device for winding the double yarn onto a package spool. A control apparatus is also Provided for interrupting the operation, with sliver detectors connected arranged in front of the drafting units and with at least one yarn detector connected arranged behind the air nozzles.
Arrangements of the initially mentioned type are known (DE-A 36 34 464--corresponding U.S. application Ser. No. 105,813, filed Oct. 8, 1987, now U.S. Pat. No. 4,790,130 and DE-A 38 00 810). If one or both slivers to be fed should break in these arrangements, this sliver breakage must be eliminated first, for example, by connecting with a newly fed sliver, before a piecing operation can be carried out.
It is also known to monitor the individual yarn components with respect to thick and thin points and to clean these out before the yarn components are guided together to form a double yarn. After the cleaning-out, a new piecing must also be carried out.
In the case of ring spinning machines, it is known (DE-A 23 39 654) to equip an automatic piecing apparatus with a device at the outlet of the drafting unit which determines whether roving is supplied at the spinning point at which a yarn breakage is to be eliminated. If no roving is present, no piecing operation is initiated. Since the emerging of roving, which is not spun into a yarn, from the drafting unit is also an indication of a yarn breakage, this signal is at the same time used as a piecing signal, i.e., as the signal which triggers the start of the operation of the piecing device.
An object of the invention is to develop an arrangement of the initially mentioned type so that it is suitable for an automatic device and so that an automatic piecing carriage can be called to the respective arrangement, as required.
This object is achieved in that the control apparatus is equipped with devices for generating a piecing signal, the piecing signal being generated after the yarn detector or detectors has/have responded or, if a sliver detector has responded, after the defect signal of the sliver detector is extinguished.
By means of this construction, it is taken into account that a piecing cannot be carried out if one or both slivers moving into the drafting units is or are broken. In this case, a piecing device does not become operative at the respective arrangement as long as the sliver breakage is not eliminated and the defect signal of the sliver detector is not extinguished. It is only when a successful piecing operation is possible that the automatic piecing carriage receives a corresponding signal so that it becomes operative.
As a rule, there will only be a sliver breakage when the sliver which is taken from a can for example, is used up. In order to draw the attention of the operator or of an automatic can changing device with an automatic sliver piecing device to this defect, it is provided in a further development of preferred embodiments of the invention that the control apparatus is equipped with devices for generating a signal which indicates a sliver defect.
In a further development of preferred embodiments of the invention, it is provided that the control apparatus is equipped with devices for the switching-on of the drafting unit which can be switched on for a given time period after the extinguishing of a signal of a sliver detector indicating a sliver defect, and that the control apparatus is connected with devices for the simultaneous activating of suction devices assigned to the outlet of the drafting units. As a result, it is ensured that the part of the sliver to which the new sliver was pieced and which represents a thick point, in most cases, is not used for producing a yarn component. The reason is that there is the risk that this thick point may result in a yarn defect which would be detected by a corresponding yarn detector and would lead to a switching-off of the corresponding spinning arrangement for the cleaning-out of this yarn defect. In this case, the piecing operation would have to be repeated within a very short time at the same spinning arrangement. However, this cannot happen before the piecing carriage, when carrying out its monitoring travel, passes by again at the respective arrangement. In the case of a large machine, this may result in a disadvantageously long stoppage time.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.